1. Field Of The Invention
This invention relates to a connector having the capacity to sense loads caused by displacements in multiple axes. Specifically, this invention relates to a connector having the capacity to both connect objects undergoing large displacements, and to provide an accurate measure of the loads caused by these displacements.
2. Description Of The Related Art
In general, where two large objects are going to be flexibly connected, there is a need to understand the forces experienced at that connection point. This information is both useful in the design of those connections, as well as in monitoring the motions and displacements of the structure after installation. At the same time, there needs to be a way to actually join the objects, for that joint to be realistic in light of the conditions likely to be experienced by that joint, and for a method of measuring the loads experienced by the joint under high displacements. For testing purposes, such a connection needs model a flexible joint being subjected to the type of force normally experienced by objects undergoing high displacements. For instance, examples of connectors undergoing high displacements include connections between oil rigs and the ocean floor or between coupled barges and ships where the oil rig, barge, or ship is being subjected to a high sea state. In addition, such a connector could be useful in modeling flexible buildings foundations being subjected to a severe earthquake.
Outside of testing, there is often a need to continuously monitor the behavior of a flexible joint undergoing high displacements to assess the health of that joint, and to use this assessment to determine whether to take corrective action to maintain the health of the joined structures. For instance, such a flexible connector would be useful in providing early warning to an oil rig should the high sea state cause unsafe stress at the connection between the ocean floor and the oil rig structure, allowing for the oil rig operators to react properly. However, the prior art is devoid of a suitable invention that both connects objects undergoing large displacements and allows for measurement of the stresses these displacements cause that connector.
First, it is known in the art to connect two objects that are undergoing large dynamic loading. For example, U.S. Pat. No. 4,717,288 teaches the use of a building joint being that is resistant to severe earthquake displacements. This joint consists of interconnected cantilever beams that provide flexibility in multiple axes. However, the joint taught by U.S. Pat. No. 4,717,288 does not teach an interconnection of cantilever beams where specific sets of beams isolate the displacements along a specific axes, which makes the sensing of loads caused by this displacements impracticable. Similarly, in U.S. Pat. No. 5,509,238, the joint utilized a series of "C" shaped springs that allows the attached structures to move in multiple axes relative to one another. However, this arrangement also fails to isolate the displacements as is needed to sense the loading that the joint is experiencing.
In addition, it is known to sense the loading of connections between objects undergoing these large dynamic motions and displacements. However, prior solutions were restricted to either measuring small displacements, or to measuring inflexible connectors. For instance, U.S. Pat. No. 3,648,514 discloses a sensing joint that relies upon a series of hollow flexural elements, with each flexural element containing a stiff internal rod. This combination attaches two structures at discrete attachment points. By combining a flexural element and a rod, this combination gives a single mechanism for measuring loads caused by displacements in three orthogonal directions. However, due to the stiffness of the internal rod, this solution is not suited for situations where the connected members are undergoing large displacements.
Similarly, in Richard Lewis, Mobile Test Design and Preparation, Presentation at the ONR Mobile Offshore Base Technology Exchange Conference (Arlington, Va.)(Sep. 22, 1998), a connector is proposed that is both capable of measuring the loads experienced by connectors linking modules in the proposed Mobile Offshore Base, and is capable of acting as a connector between these modules. The proposed connector relies upon a series of load cells connecting these modules. These load cells are arranged in an orthogonal pattern, which allows each load cell to substantially resist the displacement along either a vertical, lateral, or longitudinal direction, depending on the orientation of that load cell. To isolate the axial loads taken by the load cells, this invention also uses ball joints to prevent the load cell from resisting non-axial displacements and moments. However, this load cell arrangement is fairly inflexible and would not be suitable for modeling connected members undergoing large displacements. Thus previous joints and connectors used to measure large dynamic displacements and motions do not allow for accurate modeling of flexibly connected members undergoing large-scale displacements.
Lastly, there are other solutions to multi-axis force connector measurement available. However, some, such as U.S. Pat. Nos. 5,490,427 and 5,063,788, while capable of measuring loads experienced by a connection in multiple axes, are unsuitable to also be used as a connector between objects experiencing large displacements. Still other solutions exists such as that suggested by U.S. Pat. No. 5,129,265, which utilizes flexible mechanisms to allow for large displacements. However, this invention does not allow for loads experienced by more than two axes and is not be suitable for use as a connector between two large objects that is experiencing displacements in more than two axis. Additionally, U.S. Pat. No. 4,981,552 discloses a highly sensitive multi-axis measuring devices using leaf springs that allow for high displacement motions. However, these leaf springs are used as multi-axis measuring devices, and would not be suitable for adaptation as a multi-axis connector.
As such, there exists no suitable connector that both connects two objects undergoing large displacements and is capable of measuring the loads caused by these large displacements.